ASBI Pocket Beit Midrash: Aruch HaShulchan Laws of Synagogue 151:6

One should not sleep in a synagogue, even a nap. But it is permissible to do so in a beit midrash for one who learns there. And for the sake of the synagogue itself one can eat or sleep there but one should not bring a mattress into the synagogue. And for this reason one can sleep in the synagogue on the night of Yom Kippur in order to guard the candles so that no bad thing occur. Also those who sleep in the synagogue on Yom Kippur to guard the candles recite many Psalms and songs and praises. It is also permissible to sleep in the synagogue for a mitzvah purpose like in earlier times they would enter the synagogue to intercalculate the year and they would not return to their homes at all and would eat and sleep there. But they ate only simple foods (bread and beans). And when one makes a siyum on a massechet, and certainly if one makes a siyum on something larger, one can eat in the beit midrash since that is a se'udat mitzvah [mitzvah meal]. But to set a large meal there seems not right and one should only do so in a case of great need. And this is specifically the se'udat mitzvah of Torah study and not some other mitzvah like the meal of a bris or pidyon ha-ben or wedding. Those cannot take place in a beit midrash since they have no relevance to a beit midrash.